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24.(本题6分) 设a1=22-02，a2=32-12，…，an=(n+1)2-(n-1)2(n为大于1的整数) (1)计算a15的值; (2)通过拼图你发现前三个图形的面积之和与第四个正方形的面积之间有什么关系： __________________________________(用含a、b的式子表示); ① ② ③ ④ (3)根据(2)中结论，探究an=(n+1)2-(n-1)2是否为4的倍数. 25.(本题10分)已知：c=10，且a，b满足(a+26)2+|b+c|=0，请回答问题： (1)请直接写出a，b，c的值：a= ，b= ; (2)在数轴上a、b、c所对应的点分别为A、B、C，记A、B两点间的距离为AB，则AB= ，AC= ; (3)在(1)(2)的条件下，若点M从点A出发，以每秒1个单位长度的速度向右运动，当点M到达点C时，点M停止;当点M运动到点B时，点N从点A出发，以每秒3个单位长度向右运动，点N到达点C后，再立即以同样的速度返回，当点N到达点A时，点N停止.从点M开始运动时起，至点M、N均停止运动为止，设时间为t秒，请用含t的代数式表示M，N两点间的距离. 2018-2019届七年级数学上册期中试题含参考答案（苏科版） 一、选择题 1.A 2.B 3.A 4.C 5.C 6.D 7.A 8.D 9.B 10.D 二、填空题 11.4 12. 13.或 14. 六 15. 16.14或-14 17.37 18. 2,7,22 四、解答题 19.计算： (1)-5-(-4)+7-8 (2) =-5+4+7-8···· 20.化简： (1)3y2-9y+5-y2+4y-5y2 (2)5(3a2b-2ab2)-3(4ab2+a2b) =-3y2-5y+5·····················(4分) =15a2b-10ab2-12ab2-3a2b·········(2分) =12a2b-22ab2···························(4分) 21.(1)a2-xy×2-xy=a2-2xy;··························································(3分) (2)当a=12，x=7，y=4时， 原式=122-2×7×4=88 ···········································································(6分) 22.-4×3+2×5+0×3+1×4-3×2+5×3=11······················································(2分) 11÷20=0.55(g)，所以这批样品的平均质量比标准质量多0.55g····························(4分) (450+0.55)×20=9011(g)，所以抽样的总质量是9011g .·········································(6分) 23.(1) (50-x) (3x+600) (15x+750)····························································(3分) (2) 40(600+3x)-90×50-(750+15x)=105x+18750············································(5分) 当x=30时，原式=21900··········································································(6分) 耗水量为(3x+150)千克，当x=30时，3x+150=240，所以符合要求.······················(8分) 24.(1)a15=162-142=256-196=60·······································································(2分) (2) (a+b)2=a2+2ab+b2 ··············································································(4分) (3) an=(n+1)2-(n-1)2 =(n2+2n+1)-(n2-2n+1) =n2+2n+1-n2+2n-1=4n 是4的倍数. ···············································································(6分) 25.(1)a= -26，b=-10;···············································································(2分) (2) AB=16;AC=36;·····················································································(4分) (3)①当0≤t≤16时，MN=t， ②当16 ③当24 ④当28 ⑤当30 ⑥当36 (责任编辑：admin) |